wireless power transmission via power satellite

8/2/2019 Wireless Power Transmission via Power Satellite

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K.L.E. Societys

College Of Engineering & Technology, Belgaum-08

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Seminar on Wireless Power Transmission (WPT) Via Power

Satellite

On 15/02/2012

By

Abhishek Kumar

8thSem.

USN- 2KL08EE001


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ACKNOWLEDGMENT

Before we get into the thick of the things we would like to add

a few heartful words for the people who were part ot this repor

in numerous ways people who gave a heading support right

from the stage the report idea was conceived.

Heartful thanks to ____________________ for this untiring

and timely guidance in the completion of this report. This

active in our report helped us to achieve our goal. It is who

encouraged us to move on with the report and bring in to

success.

We are greatful to our H.O.D for valuable suggestion towardsthe successful completion of this report.

Last but not the least we heartly acknowledge the co-operation

given to us by one and all in the Electrical & Electronics

department.


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INTRODUCTION

A major problem facing Planet Earth is provision of an adequate supply of clean

energy. It has been that we face three simultaneous challenges

1. Population growth

2. Resource consumption

3. Environmental degradation.

All converging particularly in the matter of sustainable energy supply. It is widely

agreed that our current energy practices will not provide for all the world's peoples

in an adequate way and still leave our Earth with a livable environment. Hence, a

major task for the new century will be to develop sustainable and environmentallyfriendly sources of energy.Projections of future energy needs over this new century show an increase by a

factor of at least two and one Half, perhaps by as much as a factor of five. All of

the scenarios from reference 3 indicate continuing use of fossil sources, nuclear,

and large hydro. However, the greatest increases come from "new renewables"

and all scenarios show extensive use of these sources by 2050.

Indeed, the projections indicate that the amount of energy derived from newrenewables by 2050 will exceed that presently provided by oil and gas combined.

This would imply a major change in the worlds energy infrastructure. It will be a

Herculean task to acquire this projected amount of energy. This author asserts th

there are really only a few good options for meeting the additional energy needs o

the new century in an environmentally acceptable way.

Solar power captured on the Earth is familiar to all. However, an alternative

approach to exploiting solar power is to capture it in space and convey it to the

Earth by wireless means. As with terrestrial capture, Space Solar Power (SSP)provides a source that is virtually carbon-free and sustainable. As will be describe

later, the power-collecting platforms would most likely operate in geosynchronous

orbit where they would be illuminated 24 hours a day (except for short eclipse

periods around the equinoxes).


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WIRELESS POWER TRANSMISSION (WPT)

BACKGROUND:-

The vision of achieving WPT on a global scale was proposed over 100 years ag

when Nikola Tesla first started experiments with WPT, culminating with th

construction of a tower for WPT on Long Island, New York, in the early 1900s.

Tesla's objective was to develop the technology for transmitting electricity t

anywhere in the world without wires. He filed several patents describing wireles

power transmitters and receivers. However, his knowledge of electric

phenomena was largely empirical and he did not achieve his objective of WPT

although he was awarded the patent for wireless radio in 1940The development of WPT was not effectively pursued until the 1960s when th

U.S. Air Force funded the development of a microwave-powered helicopt

platform. A successful demonstration of a microwave beam-riding helicopter wa

performed in 1965. This demonstration proved that a WPT system could b

constructed and that effective microwave generators and receivers could b

developed for efficient conversion of microwaves into DC electricity

The growing interest in solar energy conversion methods and solar energ

applications in the 1960s and the limitations for producing cost-effective base loapower caused by adverse weather conditions and diurnal changes led to the sola

power satellite concept in 1968 as a means to convert solar energy with solar ce

arrays into electricity and feed it to a microwave generator forming part of a plana

phased-array antenna. In geosynchronous orbit, the antenna would direct

microwave beam of very low power density precisely to one or more receivin

antennas at desired locations on Earth. At a receiving antenna, the microwav

energy would be safely and very efficiently reconvened into electricity and the

transmitted to users. The first technical session on solar power satellites (SPS

was held in 1970 at the International Microwave Power Institute Symposium

which representatives of Japan, European countries, and the former Soviet Unio

were present. Based on preliminary studies, a plan for an SPS program wa

prepared by an NSF/NASA panel in 1972 and the first feasibility study of SPS wa

completed for NASA/Lewis Research Center in 1974

Shortly after the "oil shock" of October 1973, Japan staned to implement th


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Sunshine Plan to develop renewable energy sources. Japan's Plan included, as

long-term objective, the development of SPS. Back in the U.S. in 1975,

successful demonstration of microwave wireless power transmissions wa

performed at the NASA Deep Space Antenna facility at Goldstone, California.

this demonstration of point-to-point WPT, 30 kW of microwaves were beamed ovea distance of one mile to a receiving antenna. Microwaves were converted direct

into DC at an average efficiency of 82%, confounding critics who claimed that suc

high conversion efficiencies could not be achieved. By 1976 engineering

environmental and economic analyses of several SPS concepts had bee

performed by NASA the office of Management and Budget, in its deliberations o

the Fry 1977 budget, directed that further study of this concept be th

responsibility of the Energy Research and Development Administration (ERDA

which subsequently became the Department of Energy (DoE). The SPS ConceDevelopment and Evaluation Program (CDEP), performed by DoE/NASA and i

contractors, used a NASA-developed SPS Reference System configuration as

basis for conducting environmental, societal, and comparative econom

assessments, The DOE/NASA assessment team, as well as a majority o

scientists, engineers, and analysts who participated in the CDEP recommende

that the program be continued at a modest funding level, and SPS assessmen

directed at resolving or reducing significant uncertainties associated wi

microwave radiation effects and SPS design considerations, and to continue som

promising experiments. By 1980 the CDEP was brought to its schedule

conclusion and not continued in a follow-on program, partly because th

economic pressures of the oil crisis had passed, partly because of change

priorities for renewable energy development, and partly because of expectation

that nuclear and eventually fusion power would meet future growth in energ

demands.

A substantial body of work, both analytical and experimental, has established th

technical feasibility of wireless transmission of useful amounts of power. Wireles

transmission of power is similar in concept to information transmission b

communications satellites, but at a higher intensity. However, because the rad

frequency power beam is engineered for conversion back to electricity at very hig

efficiency, useful amounts of power could be transmitted at intensities less tha

that of sunlight. Experimental transmissions of power in amounts up to 30 kW hav

been accomplished over short distances (1.6 km) with conversion efficiencies


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excess of 85% from incoming radio frequency power into electrical powe

Recent studies indicate that collection and transmission of power from space cou

become an economically viable means of exploiting solar power within the ne

couple of decades. A substantial maturation of certain technologies is needed an

most importantly, the cost of launching material to space must be significantreduced. Very active efforts are being pursued in the aerospace community t

achieve both of these goal

Two types of WPT:1) Ground based power transmission2) Space based power transmissionBut Space-based power transmission is preferred over Ground-based power

transmission.Ground is (obviously) cheaper per noontime watt, but:Space gets full power 24 hours a day3X or more Watt-hours per day per peak wattNo storage required for nighttime powerSpace gets full power 7 days a week no cloudy daysSpace gets full power 52 weeks a yearNo long winter nights, no storms, no cloudy seasonsSpace delivers power where its needed

Best ground solar sites (deserts) are rarely near usersSpace takes up less, well, spaceRectennas are 1/3 to 1/10 the area of ground arraysRectennas can share land with farming or other uses

INTRODUCTION TO LARGE SPS:-Since 1967, Solar Power Satellites (SPS) have proposed to collect solar energy inspace and beam it down to the Earth. With the energy crisis of the early 1970's,SPS

was seriously considered as an alternative to producing electric power from fossilfuels (during the 1970s, petroleum was used to produce a significant fraction of thU.S.electric power supply). With worldwide demand for electric power increasing aswell as concern growing over urban smog and the greenhouse effect, SPS is agaattracting mainstream interest.There are several advantages to SPS. Solar radiation can be more efficiently


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collected in space, where it is roughly three times stronger than on the surface ofthe Earth and it can be collected 24 hours per day (since there are no clouds ornight in high Earth orbit). SPS does not use up valuable surface area on the Earthand can be beamed to areas with the highest demand at any particular time. Mostof these systems would utilize photovoltaic (PV) cells similar to those on Earth-based systems (such as those used by home power systems and highway signpanels). Others would utilize reflectors and mechanical collectors similar to thoseused in special large-scale solar facilities in France and the California desert(Barstow). Some PV systems would also use reflective concentrators. Most ofthese systems collect solar energy in space and transmit it via a microwave energbeam to an Earth-based rectenna which converts the beam into electricity for useon Earth. Microwave beams have a fairly low wavelength (lower than visible light)and do not appear to pose any danger to the Earth's atmosphere. In fact,telephone companies have been beaming microwaves through the atmosphere fo

over thirty years without any known problems. High launch costs, which can runroughly between $1,000 to $10,000 per pound, are the greatest barrier to thedevelopment of SPS. Most SPS proposals require launch costs of about $200 pepound to compete with your local utility company. However, growing demand forelectric power could outstrip traditional production capability, driving prices up tothe point where SPS would be competitive. If limits on producing electricity byburning coal (in order to reduce pollution) are enacted, SPS could becomecompetitive even earlier.

Four basic steps involved in the conversion of solar energyto electricity and delivery are:-1) Capture solar energy in space and convert it to electricity2) Transform the electricity to radio frequency energy and transmit it to Earth3) Receive the radio frequency energy on Earth and convert it back to electricity4) Provide the electricity to the utility grid

Using photovoltaic cells does the conversion of solar energy to electric energy.There are different types of photovoltaic cells. The single crystal silicon is one typ

of photovoltaic cell, which is formed by a doped wafer formed from a slice of singlcrystal. Though it has good efficiency it is less used due to expense factor, whichcomes in due to necessity of high grade of silicon. Its follower is poly crystallinesilicon with moderate efficiency and reduced cost. Gallium arsenide is but mostcommonly used due to high efficiency in comparison to all other types. Then thereare dynamic cells which use Solar concentrators to concentrate upon amechanical heat engine (not photovoltaic). But these are expensive and involve


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higher maintenance. Often not suitable for small applications. But they do havehigh conversion efficiencies of the range 30% and above.Developing any substantial source of energy requires the dedication of significantamounts of capital, land, technical skills, etc. The exploitation of Space SolarPower will require all of these plus some that are unique. As noted before, SSPsystems will likely operate in geosynchronous orbit. This orbit is at an altitude sucthat the platform appears to be stationary over a specific point on the surface ofthe Earth. As a result, this particular orbit is highly desirable for Earth-orientedactivities, for example communications, hence international control is exercisedover the assignment of positions or "slots" in this orbit.

TRANSMISSION:-Solar power from the satellite is sent to Earth using a microwave transmitter. Thistransmission is transmitted to the relevant position via an antenna. Thetransmission is transmitted through space and atmosphere and received on earthby an antenna called the rectenna. Recent developments suggest using laser byusing recently developed solid state lasers allow efficient transfer of power.

A range of 10% to 20% efficiency within a few years can be attained, but furtherexperimentation still required taking into consideration the possible hazards that it


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could cause to the eyes. In comparison to laser transmission microwave transmissiois more developed, has high efficiency up to 85%, beams is far below the lethal levelof concentration even for a prolonged exposure. The microwave transmissiondesigned has the power level well below the international safety standard (Frequenc2.45 GHz microwave beam). The electric current generated from the photovoltaiccells is passed through a magnetron which converts the electric current toelectromagnetic waves. This electromagnetic wave is passed through a waveguidewhich shapes the characteristics of the electromagnetic wave.Effectiveness of Wireless Power Transmission (WPT) depends on many parametersOnly a part of WPT system is discussed below, which includes radiating andreceiving antennas and the environment between them. The wave beam is expandeproportionately to the propagation distance and a flow power density is increasedinversely proportional to the square of this distance. However the WPT has somepeculiarities, which will be mentioned here. WPT systems require transmitting almos

whole power that is radiated by the transmitting side. So, the useful result is thepower quantity at the receiving antenna, but not the value of field amplitude as it isusually required. Efficiency of WPT systems is the ratio of energy flow, which isintercepted by receiving antenna to the whole radiating energy.Field distribution on the receiving antenna usually is uniform because its size is smacomparatively to the width of the beam. For WPT systems this distribution isntuniform. It has a taper form and it depends on the field distribution on the transmittinantenna.For increasing of the energy concentration on the receiving antenna the phasedistribution on the radiating antenna has usually a spherical form with the center inthe point on crossing of the receiving plate and the radiating axis. Radiating antennaof the WPT systems usually has a taper distribution of the field. This distributionallows to increase the efficiency and to decrease the field out of the receivingantenna.The efficiency of energy transmission is expressed by the functional 2. To increasethe field distribution on radiating aperture is made as a tapered distribution. Highvalue of is supposed to be in the majority of known projects of the WPT systems.However, the effectiveness of the WPT system is defined not only by the value of . Itis also determined by the rectangularity of the field distribution on the radiating

aperture, the rectangular distribution factor in the theory of antennas is usually calledthe surface utilization factor . The meaning of these two parameters and is discrepanbecause to increase 2 it is necessary to have the field falling down to edges, but toincrease it is necessary to have a uniform field.To increase the effectiveness of WPT system it is necessary to increase the product2, though the requirements for each of both multipliers are opposite. This product isnamed a generalize criterion! It is possible to find the way out of this contradiction if


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the antenna is discontinuous (discrete) one. Let us produce the field distribution in thradiating discrete antenna falling to its edges not by means of creation of non-uniformdistribution of the field but with the help of irregular situation of identical subapertures, each of them having the uniform field distribution. It is supposed that thenumber of these apertures is sufficiently high in order to admit the approximation ofthe integral optimum monotonous Gauss distribution by means of step function. Theplaces of sub aperture disposition can be found by the differentiation of this stepfunction. Discrete distribution of sub apertures presents non-equadistant antennaarray consisting of the similar elements. Such optimization is optimal inChebyshevs sense since the maximum error tends to zero while the number ofsub apertures is tended to infinity. So the field in the place of observers dispositiowould be similar to step and the monotonous signal source. The falling to the edgefield distribution is typical for the WPT problems. For the discrete-step distributionsthat means the concentration of sub apertures in the center and their gradual

discharge on the edges. Thus all sub apertures are similar and have the uniformdistribution of the field with the equal amplitude, which may reach the maximumadmissible value.The dismemberment of continuous apertures and slight moving of them apart in thespace when all of apertures are equal and uniformly feed increases theireffectiveness (the generalized criterion is increased). The generalized criteriondetermines the quality of the WPT Systems better than usual criterion. The optimaldistribution form may be reached for the large radiating apertures wheredismemberment at many parts is easily realized by disposition of sub aperture clots places, which correspond to high field intensity (first of all it concerns the center of thradiator) and relieving sub aperture density at edges of antenna. This constructionallows to approach to unit the value both of coefficients 2 and . As a result theeffectiveness of the WPT system will be essentially increased.For receiving these transmitted waves rectennas are set up at the Earth. An antennacomprising a mesh of dipoles and diodes for absorbing microwave energy from atransmitter and converting it into electric power. Microwaves are received with about85% efficiency and 95% of the beam will fall on the rectenna but the rectenna isaround 5km across (3.1 miles). Currently there are two different design types beinglooked at- Wire mesh reflector and Magic carpet. Wire mesh reflector type rectennas

are built on a rigid frame above the ground and are visually transparent so that itwould not interfere with plant life whereas in the magic carpet type material pegged tthe ground.


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CHALLENGES:-The development and implementation of any new energy source present major

challenges. And it is acknowledged that bringing about the use of Space SolarPower on the Earth may be particularly daunting because it is so different. Themajor challenges are perceived to be:(1) The mismatch between the time horizon for the implementation of SSP andthat for the expansion of conventional energy resources(2) The fact that space power is intrinsically global, requiring enterprise modelsthat give every player a suitable stake and adequate safeguards(3) The potential for concerns over reliability, safety and environmentalimplications

(4) The need to obtain publicly-allocated resources outside the normal purview ofthe energy community(5) The prevailing mind set which tends to view the future energy infrastructure asan extrapolation of the present one.However great the challenges, it is important to enhance global energy systems sthey work for all the people of the Earth. It is asserted that a prudent course wouldbe to give serious attention to all plausible options and prepare to implementseveral if needed.It is well understood that something as vast as the global energy system canchange only slowly. In fact, it takes from 50 to 75 years for one source to lose

dominance and be replaced by another. Even if it is recognized and agreed that ashift to different sources is needed, penetration would be slow.The time horizon for implementing Space Solar Power will be at least a couple ofdecades. Current work being carried out in the US by the National Aeronautics anSpace Administration (NASA) and in Japan by the Ministry of Economy, Trade anIndustry (METI) indicate that demonstrations of space-to-ground transmission ofpower could come in the current decade and initial commercial power delivery in


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about 20 years. A significant contribution in terms of global energy would clearlytake substantially longer. The challenge presented by this mismatch can beaddressed in two ways:First, governments will need to underwrite, to a major extent, the R&D needed tobring the enabling technologies to maturity. Governments havetraditionally supported R&D efforts as a spur to new economic activity. Examplescan be found in the development of rail and air transport systems, computers andmost recently, the internet.Second, a near-term involvement by the users (the electric utilities and theirsuppliers) should be promoted. It is very important for these prospective users tokeep abreast of progress as the technology matures.The global scope of Space Solar Power will present another significant challengein terms of appropriate enterprise models that give every player a suitable stakeand adequate safeguards. International cooperation in the energy area is

commonplace and indeed the infrastructure for energy is highly interdependentaround the world. Energy acquisition, distribution, and utilization tend to involvemultiple countries and far-flung networks along which various forms of energy flowimilarly, international collaboration has been important in major space ventures ofwhich Space Solar Power would certainly be an example.Briefly, there are several reasons for international collaboration. The mostcompelling are:The need for increased energy supplies is a global needThe impact on the environment of present energy practices is a matter ofworldwide concernInternational coordination in energy provisioning is common today and theinterdependence will only grow in the futureThe needed technology is widely distributed and no one country has all thecapabilityThe large scale of Space Solar Power will require international financingInternational regulations control critical resources, specifically slots ingeosynchronous orbit and appropriate transmission frequenciesRecognition of Space Solar Power as a viable and safe approach to energy willrequire an international consensus.

Space Solar Power is perceived as very different from all other power sourcesbecause of its wireless delivery. A significant challenge will be to allay concernsabout the safety of this transmission mechanism. A substantial body of theoreticaand experimental work exists and this work indicates that, for the power densitylevels being considered for importation of power from space, there are notroublesome effects to life forms. Since radio frequency power is non-ionizing, theonly likely effects are thermal and these should be modest in view of the fact that


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the intensity of the transmitted beam Space Solar Power is perceived as verydifferent from all other power sources because of its wireless delivery. A significanchallenge will be to allay concerns about the safety of this transmissionmechanism. A substantial body of theoretical and experimental work exists andthis work indicates that, for the power density levels being considered forimportation of power from space, there are no troublesome effects to life forms.Since radio frequency power is non-ionizing, the only likely effects are thermal anthese should be modest in view of the fact that the intensity of the transmittedbeam.Developing any substantial source of energy requires the dedication of significantamounts of capital, land, technical skills, etc. The exploitation of Space SolarPower will require all of these plus some that are unique. As noted before, SSPsystems will likely operate in geosynchronous orbit. This orbit is at an altitude sucthat the platform appears to be stationary over a specific point on the surface of

the Earth. As a result, this particular orbit is highly desirable for Earth-orientedactivities, for example communications, hence international control is exercisedover the assignment of positions or "slots" in this orbit.The changes in dominant source over time were noted in an earlier figure and wesee a continuing change. Considering the relative role of the various sources ove

just the last century, we have seen the prominence of wood vanish and that of codiminish greatly. At the same time, the contributions of oil and gas rose fromvirtually nothing to dominance, and nuclear became a significant contributor in amatter of only 25 years.Today we the opportunity and the challenge to create a future that is energy-richand sustainable, but we must be open to a departure from past and presentpractices and expect that the energy situation in 2100 will be very different fromthat of today.The prudent response is a pro-active assessment of all reasonable options andpursuit of those that appear most viable, however futuristic they may seem atpresent.

ADVANTAGES:-

1. Unlimited energy resource2. Energy delivered anywhere in the world3. Zero fuel cost4. Zero CO2 emission5. Minimum long-range environmental impact6. Solar radiation can be more efficiently collected in space


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DISADVANTAGES:-1. Launch costs2. Capital cost even given cheap launchers

3. Would require a network of hundreds of satellites4. Possible health hazards5. The size of the antennas and rectennas6. Interference with communication satellites

EVOLVING WPT MARKETS:-Markets that will be made accessible with WPT will have a profound influence on

global business activities and industry competitiveness. The following are

examples of the future commercial opportunities of WPT:

1. Roadway powered electric vehicles for charging electric batteries with WPTfrom microwave generators embedded in the roadway while a vehicle is travelingat highway speed, thus eliminating stops to exchange or recharge batteries greatlextending travel range.

2. High-altitude, long-endurance aircraft maintained at a desired location for weekor months at 20 km for communications and surveillance instead of satellites, at

greatly reduced costs.

3. Power relay satellites to access remote energy sources by uncoupling primaryelectricity generation from terrestrial transmission lines (15). Power is transmittedfrom distant sites to geosynchronous orbit and then reflected to a receiver on Earin a desired location.

4. Solar power satellites in low-Earth or geosynchronous orbit or on the Moon tosupply terrestrial power demands on a global scale.

CONCLUSION:-There is little doubt that the supply of energy must be increased dramatically incoming decades. Furthermore, it appears almost certain that there will be a shifttoward renewable sources and that solar will be a major contributor. It is asserted


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that if the energy system of the world is to work for all its people and be adequaterobust, there should be several options to develop in the pursuit of and expandedsupply. While the option of Space Solar Power may seem futuristic at present, it istechnologically feasible and, given appropriate conditions, can becomeeconomically viable. It is asserted that it should be among those options activelypursued over coming decades. The challenges to the implementation of SpaceSolar Power are significant, but then no major expansion of energy supply will beeasy. These challenges need to be tackled vigorously by the space, energy andother communities.Finally, it should be emphasized that if we fail to develop sustainable and cleanenergy sources and try to limp along by extrapolating present practices, the resultis very likely to be thwarted development of economic opportunities for many of thEarth's people and, almost certainly, adverse changes to the planetaryenvironment.

REFERENCE:-P.E. Glaser Method and Apparatus for Converting Solar radiation toElectricaPower, U.S. Patent 3 781 647, 1973.R. Bryan Erb, "Space-Based Solar Power - How Soon and How Much", 49th

Congress of the International Astronautical Federation, Paper IAF-98-R.2.02,

Melbourne, Australia, September 28 - October 2, 1998.

WEC/IIASA, Global Energy Perspectives, Nakicenovic, Nebojsa, et al, Cambridge

University Press, 1998.

P. E. Glaser, "An overview of the solar power satellite option," IEEE Transactions

on Microwave Theory and Techniques, vol. 40, no. 6, pp. 1230-1238, June 1992.

W. C. Brown and E. E. Eves, "Beamed microwave power transmission and its

application to space," IEEE Transactions on Microwave Theory and Techniques,

vol. 40, no. 6, June 1992.

World Energy Council, "Energy for Tomorrows World - Acting Now", WECStatement 2000,http://www.worldenergy.org.

http://www.nspri.com
http://www.worldenergy.org/http://www.worldenergy.org/http://www.worldenergy.org/http://www.nspri.com/http://www.nspri.com/http://www.nspri.com/http://www.worldenergy.org/

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